A technology for detecting an undesirable driver state in terms of a driving operation, such as looking aside while driving and drowsy driving, has been developed. In such a technology, the face of the driver is photographed with a camera to obtain a facial image of the driver and the facial image is analyzed to detect the driver state (e.g., JP-2003-296712A, JP-2008-123137A corresponding to US2009/0251534A, JP-3316725B corresponding to US-5801763B, JP-2009-116797A corresponding to US2010/0254571A, and JP-2008-276328A corresponding to US2008/0267600A).
For instance, the positions of eyes (e.g., black eyes or pupils) of a driver are detected to detect a looking-aside state. The open/closed states of eyes (eye lids) of the driver are detected to detect sleepiness.
In order to obtain a stable image in taking the image with the camera, a light source (projector) radiates a necessary amount of light (e.g., infrared light) toward the face and its surroundings by, e.g., pulse lighting.
However, the inventor of the present application has found out that if the driver is wearing a pair of eyeglasses, it is difficult to highly accurately obtain eye-related information such as the positions of eyes, the open/closed states of eyes, or the like.